Method of surfacing metallic articles



Patented May 8, 1?5l OFFICE? j METHOD OF SURFACING METALLIC ARTICLES Adolph W. Machlet, Elizabeth, N. J.

No Drawing. Application January 11, 1949, Serial No. 70,378

2 Claims. 1

This invention relates to corrosion-inhibiting treatments and it is more especially concerned with causing a tough coating or finish in the nature of a surface alloy on ferrous articles such as articles made of iron or alloys thereof which normally tend to corrode or rust upon exposure to air and humidity.

Various treatments for rust-proofing iron have been resorted to but as they are well known they need not be detailed except to observe that all possess characteristic failings either with respect to involved operations, to undesirable finish, or to short-life protection, etc.

My extended researches have led to the discovery of a simple and direct method of imparting to ferrous articles, a surface which resists corrosion, staining or rusting to a pronounced degree and, at the same time, exhibits an attractive finish which is glossy and hard and tough and of a bluish-black color. This surface or skin may be quite thin or even of considerable thickness, as the case may be, and is uniformly spread on all the configurations of the articles and as it is in the nature of an alteration of, rather than an addition to the metal of the articles, it does not appreciably alter the original dimensions thereof or produce any undesirable roughness; a highly important factor with respect to screw-threads and the like.

' In carrying out my method, a mixture is first made of some fine carbon together with a finely divided ore or residue thereof. As set forth in my two co-pending applications executed and filed of even date herewith Serial Numbers 70,379, now U. S. Patent No. 2,529,344, and 70,380, now U. S. Patent No. 2,529,345, each filed January 11, 1949, the carbon may be of the familiar form well-known as charcoal. Especially suitable for this purpose is the residue resulting from the extraction of aluminum from bauxite, or other alumina bearing earths. This waste material is known as red-mud and is a dampish waste product available at no cost in large quantities. It usually analyzes about 18% to 25% of alumina which has resisted the extraction process together with 13% to 20% ferric oxide, 7% to 12% titanium oxide, silica to 15%, lime 10% to 18% and soda 4% to 7%. The loss on ignition during analysis is about 14% to 17% which may be said to be mostly water.

The aforesaid material may be employed as such; or it may be used, together with metallic scrap such as brass chips or metal-bearing residues from ores or treatments thereof, especially such residues as are unprofitable for usual metalextraction methods.

The articles to be surfaced are placed in a furnace or retort together with enough of my mixture to cover them, and are preferably tumbled with it while the temperature is being increased to a range of from 850 F. to around 1600 F. The lower temperatures are resorted to when the articles to be finished have been heat-treated and it is not desirable to materially diminish the hardness thereof. Otherwise, the higher temperatures are desirable.

During theheating in the retort, there occurs an initial emission of steam if the damp mud be used and this expells all of the free air, before the ultimate temperature is attained, but not if the material be predried. As the temperature is further increased, there occurs a less pronounced emission of steam of any residual water of crystallization which may be or less decomposed by reaction with the heated carbon.

While being intimately contacted in the retort with the admixture, secondary reactions occur with the surfaces of the articles; the nature asd character of which depend upon the metal of the articles and the ingredients of the mixture. In all cases, however, a tough skin results the thickness of which depends upon the duration of the heating. This skin is in the nature of an alloy, especially if metallic scrap be used in the mixture. The minute metallic particles are brought into intimate physical contact with the articles and, as this occurs in a reducing atmosphere and under rubbing conditions, local alloying occurs. An agglomeration or adsorption ensues so that the skin or coating is uniform and will be found to have a relatively low coefficient of friction; a desirable characteristic. The mass is then permitted to cool while excluding air, ether in the retort, or in a closed container into which the mass is dumped. When the temperature falls to a moderate degree, the articles are then removed, and may then be scratch-hushed or tumbled to eliminate the dust thereon.

No further treatment is required, and the articles will be found to have a superior finish as above mentioned.

I claim:

1. A process of rendering ferrous articles resistant to corrosion consisting in mingling them in a powdery mixture of red-mud and charcoal, tumbling said mass in a retort while gradually elevating the temperature to between 850 F. and

1600 F. and then causing said mass to cool in the absence of air in a closed container.

2. A process of rendering ferrous articles resistant to corrosion, consisting in mingling them in a powdery mixture of red-mud and charcoal, together with some brass-chips, tumbling said mass in a retort while gradually elevating the temperature to between 850 F; and 1600 F. and then causing said mass to cool in the absence of air in a closed container.

ADOLPH W. MACHLET.

REFERENCES CITED UNITED STATES PATENTS Name Date Baldwin Mar. 13, 1898 Number 

1. A PROCESS OF RENDERING FERROUS ARTICLES RESISTANT TO CORROSION CONSISTING IN MINGLING THEM IN A POWDERY MIXTURE OF RED-MUD AND CHARCOAL, TUMBLING SAID MASS IN A RETORT WHILE GRADUALLY ELEVATING THE TEMPERATURE TO BETWEEN 850* F. AND 1600* F. AND THEN CAUSING SAID MASS TO COOL IN THE ABSENCE OF AIR IN A CLOSED CONTAINER. 